UK light-heavyweight Buatsi earned a win yet underwhelming beginning to life under new promoters with a unanimous decision over Zach Parker in the Manchester arena.
The Olympic medal winner's work rate appeared to earn him a judges' verdict in a tight 10-round fight at the boxing arena.
But Parker landed significant shots, landing some telling individual punches in a match where the styles failed to mesh, with excessive holding spoiling the action.
The officials had it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my greatest display but how do champions respond? They win," the victor said in the ring as he was faced negative reactions from the spectators.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in February - to secure a 20th pro success.
Some ringside observers thought Parker, thirty-one, deserved the win but the contender endured the second defeat of his 28-match professional journey.
Buatsi Secures Victory in Uneventful Affair
The fighter's advancement has slowed in recent times through management issues and long spells of inactivity.
Once tipped as the future of UK boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a ultimate opportunity - under new promotional backing.
He opened tentatively, with the two boxers ready to be aggressive in a calculated early stages.
Parker, whose sole prior loss came at the lower weight class against John Ryder in 2022 after suffering a hand injury in the contest, was making just his second fight at light heavyweight.
By the middle rounds, the underdog had made it competitive, creating difficulties for the favorite, who operated with a protective stance to barely take the cleaner periods.
The audience's tolerance decreased amid regular grabbing, with the challenger slipping to the canvas multiple occasions during close exchanges.
Parker ended stronger, but several stanzas were hard to judge. However, ex-champion Carl Frampton - providing analysis for Dazn - had it significantly in favor for Parker, scoring for Buatsi just one round.
The victor progresses, but with the likes of hard hitter David Benavidez, and Russian champion Dmitry Bivol dominating the weight class, the journey to titles - on this evidence - still seems difficult.
Ricky Hatton Memorial Fuels Local Rivalry Battle
In the secondary fight, Lyndon Arthur beat Bradley Rea by close verdict in a terrific Manchester vs Manchester fight to capture the continental championship.
The arena became quiet for a deeply poignant memorial prior to the bout as ten bells tolled in memory of local hero Ricky Hatton, who succumbed 46 years old in last month.
It was the first major televised boxing event in the urban center since Hatton's passing. As the concluding sound disappeared, the stillness gave way to a roar of "only one Hatton".
The competition during the bout reflected the feeling. The eventual winner was knocked down by a left hook flush on the chin in the early round, standing uncertainly to his feet on the eight count.
But the Manchester United-red attire of Arthur soon came forward again. Across the ring, the opponent - in opposing blue - was marked up quickly, significant bruising appearing under his face as the pair landed punishing blows.
Rea, 27, delivered effective strikes but Arthur, thirty-four, matched the intensity with powerful upward punches as the pace rarely dropped over the full distance.
Arthur edged the decision with scoring tallies of 114-114, narrow lead and clearer margin, but the two athletes were persistent and full of heart, all the qualities their hero the legend stood for.
